Which of these numbers is composite? ${7,\ 19,\ 23,\ 43,\ 63}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 7, 19, 23, and 43 each have only two factors. The factors of 63 are 1, 3, 7, 9, 21, and 63. Thus, 63 is the composite number.